Study: Blueberry leaf extract can add shelf life

Blueberry leaves contain a substance that can be added to the fruit's coating and extend its shelf life, according to an Oregon State University researcher.

Food science and technology professor Yanyun Zhao, collaborating with Chinese scientists, found an edible coating containing blueberry leaf extracts helped delay decay and retain water, slowing deterioration.

"Normally blueberry leaves fall to the ground as waste," Zhao, who's also a value-added food products specialist with the university's extension service, said in a news release. "We've discovered a use that can change how the berries are stored (and) sold, as well as increasing their nutritional value."

Weight retention also matters because blueberries are often sold by volume. The coating can facilitate washing and preparation of fresh blueberries as ready-to-eat products, the researchers found. Most blueberries are sold unwashed because rinsing them removes a natural waxy coating that preserves the fruit. Coating blueberries will add to their cost, Zhao said, but it's unclear how much.

Blueberry leaves contain antioxidant phenolics, which protect against fungi and bacteria such as E. coli and salmonella. To create the coatings, researchers mixed phenolic extracts with chitosan, a preservative that comes from crustacean shells.

Oregon State University tested coatings made from leaves picked at different stages of berry maturity. Leaf extracts were formulated into five different coating treatments based on varying phenol levels.

Blueberries were dipped in the liquid coating and dried at room temperature. Commercially, nozzles could spray the coatings on the surface of berries as they pass by on a conveyor belt.

The study was published in a pair of journals, Food Control and Postharvest Biology and Technology. Collaborating researchers included Yun Deng at Shanghai Jiao Tong University in China.